Index

Radeon Toxic HD 4870 is a name for Sapphire's special version of the HD 4870, this time with special cooling and an overclocked core. The card uses Vapor-X cooling that does a great job at 780MHz core speeds and 1000MHz memory (4000MHz effectively). Note that the reference cards run at 750MHz core and 900MHz memory (3600MHz effectively).

Today’s card comes with 512MB of GDDR5 memory, but as of January this year, the same card is available with 1GB of GDDR5. Additional memory pays off at high resolutions and in texture-intensive games, which are growing in numbers buy the way. To make things even more interesting, we’re soon expecting Sapphire to announce its HD 4870 with 2GB of GDDR5.

The Toxic HD 4870 looks quite nice with black cooling and a large fan. The fan blows the air out of the case, and as you can see from the pictures, it uses 3 heatpipes to maximize cooling efficiency.

We’re no strangers to Vapor-X cooling, and cooling the 55nm RV770 GPU as well as the rest of the card won’t be a problem whatsoever. Vapor-X uses vapor chamber technology, and it has proven its worth on Sapphire’s cards using it up to date. However, unlike the old cooler, the new one uses three heatpipes to improve cooling even further.

Vapor-X’s operation is similar to classic heatpipe technology, but many claim it’s more advanced as it uses only clean water and the vaporizing process. In the process of cooling, the water turns to steam, which fills up the vacuum chamber. The air pressure within the chamber is extremely low which enables for quick water vaporization. The GPU touches the vacuum chamber directly, and it acts as the heat source which heats up the vaporization wick. The resulting steam moves freely in all directions, towards the cooler part of the chamber and through the heatpipes, where upon touching the cold walls turns to water again. Condensation module gathers water and the transportation module brings it back to start the process over again.

The picture below shows the HD 3870 Atomic’s cooler, which hasn’t got three heatpipes. In its case, the memory was touching the chamber as well, whereas HD 4870 Toxic’s memory is cooled by touching the cooler’s aluminum body.

Before we move onto the results we’ll share some facts regarding the card’s technical points. Radeon HD 4870 is on the market for more than six months, but it’s still the best single GPU Radeon and most certainly not lacking in performance. This card came as the successor to ATI's HD 3870 card, and thanks to the RV770 it is much, much faster. This chip packs almost a billion transistors, comes with 800 scalar processors (320 on HD 3800 series) and GDDR5 memory.

Coupling the 256-bit memory interface with GDDR5 memory was the best way to provide enough bandwidth for this card to give its competition a hard time. HD 4870’s muscle is evident when compared to the Geforce GTX 260, where Nvidia had to enable additional SPs (stream processors) to keep up with the HD 4870. Note that the first GTX 260 had 192 SPs, whereas Nvidia upped the ante and now there are 216 of them.

Compared to GDDR3/4 memory, GDDR5 memory offers twice the bandwidth per pin at same clocks. This means that 512-bit GDDR3 cards offer the same bandwidth as 256-bit GDDR5 cards, provided they run at same clocks of course.

As far as HD 4870’s bandwidth goes, Qimonda’s GDDR5 memory at 900MHz does a good job to keep the card competitive against the GTX 260, which has a wider 448-bit memory bus and 999MHz memory. GTX 260’s bandwidth is 111.9GB/s whereas HD 4870 offers a slightly better bandwidth of 115.2GB/s. Radeon HD 4850 with its GDDR3 memory at 993MHz offers a bandwidth of 63.6GB/s, due to its 256-bit memory interface. By overclocking the memory, Sapphire increased the Toxic card’s bandwidth as well, and it’s now up from reference 115.2GB/s to 128.0GB/s.

Radeon HD 4870 is based on RV770 55nm GPU. Apart from 800 shader processors, which is 2.5x more compared to the previous generation, the RV770 also offers 2.5x more texture units, as there’s 40 of them now compared to the 16 on HD 3800 series. The rest of the important specs can be seen on the GPU-Z picture above.

Sapphire’s dual-slot cooling does a better job than the reference cooler. The fan is inaudible when the card is idling, but the noise levels match those of the reference card when it’s under a workload. RPM is dynamically controlled depending on the core temperatures, but you can control the directly from the Catalyst Control Center – Overdrive panel if you choose to.

Radeon Toxic HD 4870 is up to 30 °C cooler than reference. Idle mode results in core temperatures of 46 °C, but when we put the card through its paces the temperatures rose only to 59°C, unlike the reference card which hits up to 89°C.

The card depends on two 6-pin cables for power, and you’ll find the connectors to be located towards the end of the card, just like on the reference cards.

All the HD 4xxx series cards provide 7.1 sound thanks to Realtek’s HD Audio processor integrated into the GPU silicone. There’s no need for additional cables in order to bring audio via the HDMI cable as well, which is the case with Geforce cards. You can get HDMI via the provided DVI-to-HDMI dongle. The I/O panel features two dual-link DVI outs and S-Video out.